Rocket Experiment Research Articles

Variation of the Altitude of Auroral Emission During a Substorm Cycle: Stereoscopic Optical Observations During the LAMP Rocket Experiment

AbstractWe estimated the altitude of aurora by combining data from all‐sky cameras at multiple places which were obtained during the LAMP sounding rocket experiment in Alaska on 5 March 2022. During the launch window of the rocket, three high‐speed all‐sky cameras were operative at three stations immediately below the trajectory of the rocket: Poker Flat, Venetie and Fort Yukon. The all‐sky cameras captured all‐sky images with a temporal resolution of 100 Hz (80 Hz for the Fort Yukon case). The method of altitude determination is based on analyses of time‐series of the optical intensity obtained from the all‐sky cameras in Venetie and Poker Flat covering the downrange area of the rocket trajectory. The estimated altitude of pulsating aurora during the rocket experiment was found to be consistent with that derived from the in‐situ observation of precipitating electrons with a model of optical emission, which confirms the feasibility of deriving the emission altitude through correlation analyses using time‐series. The estimated altitude of aurora decreased after the expansion onset of the substorm and stayed slightly below 100 km during the interval of pulsating aurora in the recovery phase. In particular, prompt and brief lowering of the auroral emission, well down to around 90 km, was detected during a transition of auroral form from discrete to diffuse which occurred ∼10 min after the onset. This result implies an existence of a process causing harder electron precipitation operative soon after the start of the expansion phase of auroral substorm.

Microgravity Effect on Pancreatic Islets.

We previously demonstrated that boundary cap neural crest stem cells (BCs) induce the proliferation of beta-cells in vitro, increase survival of pancreatic islets (PIs) in vivo after transplantation, and themselves strongly increase their proliferation capacity after exposure to space conditions. Therefore, we asked if space conditions can induce the proliferation of beta-cells when PIs are alone or together with BCs in free-floating or 3D-printed form. During the MASER 15 sounding rocket experiment, half of the cells were exposed to 6 min of microgravity (µg), whereas another group of cells were kept in 1 g conditions in a centrifuge onboard. The proliferation marker EdU was added to the cells just before the rocket reached µg conditions. The morphological assessment revealed that PIs successfully survived and strongly proliferated, particularly in the free-floating condition, though the fusion of PIs hampered statistical analysis. Proliferation of beta-cells was displayed in 3D-printed islets two weeks after µg exposure, suggesting that the effects of µg may be delayed. Thus, PIs in 3D-printed scaffolds did not fuse, and this preparation is more suitable than free-floating specimens for morphological analysis in µg studies. PIs maintained their increased proliferation capacity for weeks after µg exposure, an effect that may not appear directly, but can emerge after a delay.

Exploring Students Potential and Creativity Through Science Exploration with Water Rockets and a Stunning Interactive Approach

<div class="page" title="Page 1"><div class="layoutArea"><div class="column"><p><span>A water rocket is an educational game that requires propulsion in the form of air and water pressure. In water rockets, the air of a room will press in all directions and water flows towards lower pressure. The purpose of this research is to analyze the effect of different elevation angles and water volume on the farthest distance of parabolic motion of water rockets. This research uses an experimental study method conducted by 2nd semester students of PSDKU PGSD Kebumen. Data collection techniques using practicum and documentation. Data analysis techniques were carried out with water rocket experiments 3 times. The experimental results showed that: 1) To produce the farthest distance traveled, the water rocket uses an elevation angle of 60 ° with a fixed water volume of 400 ml. 2) The farthest distance using a volume of 600 ml with a fixed elevation angle of 45°. The results of this study can be used as student materials for science exploration and interactive approaches so as to explore the potential and creativity of students. </span></p></div></div></div>

Early detection of combustion instabilities in liquid rocket engines: Assessment of statistical, recurrence, and fractal analyses for sub- and supercritical pressure conditions

Safe shutdown of a liquid rocket engine in ground testing prior to the onset of damaging combustion instabilities through reliable detection of instability precursors would translate to time and cost savings in engine development programmes. Methods derived from statistical, recurrence, and fractal analysis have been successfully applied in the literature to detect precursors in unsteady pressure signals from canonical combustion experiments, gas-turbine combustion experiments, and sub-scale rocket combustion experiments operated at low pressures. In the present work, several such methods were applied to data from two cryogenic oxygen-natural gas rocket experiments operated at higher pressures than previously reported; both sub- and supercritical with respect to oxygen. The goal was to identify methods that can discern limit-cycle instabilities from intermittently unstable operation and are sufficiently responsive to be applied as emergency shut-down criteria in engine tests. Among the methods applied were the standard deviation, variance of the auto-correlation, the second spectral moment, the ratio between determinism and recurrence rate, the Hurst-exponent, and the multifractal range. The second spectral moment, the Hurst-exponent, and a measure derived from the multifractal spectrum all have short detection delays for instability onset and short-lived could be discerned from self-sustaining instabilities with an appropriate choice of threshold value. They also have moderate computation cost which makes them of interest for potential real-time implementation. The Hurst-exponent has the additional advantage of a common threshold value for all test cases addressed, demonstrating its potential for broader application independent of combustion device or operating conditions.

Combustion behavior of NMP-001, a nitromethane-based green rocket propellant

Hydrazine’s carcinogenic and toxic nature makes its use in space propulsion expensive and necessitates careful launch campaign planning, which may cause delays. One already established alternative is to use energetic salt-based ionic solution propellants. However, the costs remain high because these salts are costly and highly regulated energetic materials. Additionally, propellants based on these energetic salts produce much higher temperatures during decomposition and combustion, as is the case for hydrazine. Consequently, expensive refractory metal-based alloys and high-temperature oxidation-resistant catalytic reactors must be used, which further drives up the costs. Alternatively, hydrogen peroxide may be used, though only in applications with a low specific impulse requirement. This study explores an alternative approach: using nitromethane, a commonly available laboratory solvent. NMP-001 is a nitromethane-based monopropellant that contains additives that allow for low-pressure combustion and reduce sensitivity to mechanical stimuli. Multiple combustion chamber configurations with varying characteristic lengths were tested in rocket combustion experiments. With the 11.5 m L∗-configuration, a 15.1 bar low-pressure limit could be determined. The 7.3 and 5.0 m L∗-configurations yielded a 16.2 and 28.3 bar low-pressure combustion limits, respectively. These outcomes are significantly below the 30 bar limit reported in the literature. Despite using only a simple heat-sink combustion chamber with a non-sophisticated injector element and a non-optimized propellant formulation, combustion was 83 to 95 % efficient with a C* ranged between 1133 to 1302 m/s. These figures are higher than for hydrogen peroxide and are comparable to the theoretical performance of state-of-the-art green liquid monopropellants.

A low-energy particle experiment for both ion and electron measurements using a single microchannel plate-based detector

We have developed a low-energy particle experiment that alternately measures ions and electrons in space. The ability to switch between ion and electron measurements is achieved by simply adding ultra-thin carbon foils and positive and negative outputs to a conventional top-hat electrostatic analyzer and a high-voltage power supply, respectively. The advantage of this experiment is that it can perform both ion and electron measurements using only one MCP-based detector for electrons, since it detects secondary electrons emitted from the carbon foils. For the SS520-3 sounding rocket program, we prepared two identical energy analyzers, one for ions and the other for electrons to demonstrate this technique. Laboratory tests confirmed that the performance of the two analyzers was comparable to that of conventional analyzers for ion and electrons. The SS520-3 rocket experiment in the high latitude auroral region yielded observations that captured typical features of ions and electrons, which were similar to previous observations.Graphical

Ionospheric Fireworks Illuminate Auroral Science

A sounding rocket experiment set off a spectacular nighttime light show over Scandinavia as it produced new insights into ionospheric behavior near an aurora.

Experimental astronomical observation using a lobster eye optics

AbstractA lobster eye (LE) is a wide‐field type of X‐ray optics, which provides a large field of view at the expense of angular resolution. The optics presented in this paper are the LE optics in Schmidt arrangement made from glass sheets with golden reflective coatings. It was used as a scientific payload on the WRXR rocket experiment. Before the mission itself, the optics was tested on ground to obtain more information about its behavior. Part of these tests were several nights of observation at the Ondrejov observatory. We used the optics in combination with a CMOS camera to acquire images in visible light of various bright sources in the sky. In order to enable long‐time exposures, the robotic mount of the BART telescope was used. The goal of this experiment was to confirm the focal length of the optics using a source at infinity, and to show how the optics, designed for X‐ray observations, performs in visible light. This brief article describes the methods used for evaluation and presents and discusses the results obtained within the night observation experiment.

Discovery of a German V-2 Rocket Fall Site in the Area of Chodzież, in Greater Poland

In the 1930s, in the town of Peenemünde on the northern edge of the Usedom Island in the Baltic Sea, the Germans established a military research centre to work on rocket engines. In Peenemünde, the Aggregat 4 – the first ever rocket to cross the space frontier – was constructed and launched. However, it went down in history under the name V-2. This weapon was the world’s first ballistic missile used in combat. At the end of World War II, V-2 rockets were a technological marvel of the time. Reaching supersonic speeds, they were an unrecognized design for the Allies in terms of control and targeting principles. They were a weapon almost impossible to shoot down. The RAF’s destruction of the Peenemünde facility in 1943 was the reason for its relocation to the Heidelager military training ground in the village of Blizna, Subcarpathian province, out of the range of Allied aviation. Threatened by the Soviet Army’s offensive, it was moved again in 1944 to the Heidenkraut training ground in Wierzchucin, Kuyavia-Pomerania province. As a result of archaeological work in the area of Chodzież, in northern Greater Poland province, the so far unknown site of the fall of a German V-2 rocket fired from the Heidekraut training ground, from a distance of 108 kilometres, has been located. Analysis of the finds, the appearance of the fall site and GPR surveys lead to the conclusion that a version of the rocket with little or no explosive material exploded in Chodzież. The current state of research into the active use of the Heidenkraut training ground at the end of the War leads to the conclusion that the Chodzież region, located in northern Greater Poland, was a zone of not very intensive experimental firing of V-2 rockets. Much more intensive was the firing of the Kalisz region located in southeastern Greater Poland. Further research into the sites of V-2 rocket falls both in Greater Poland and in other parts of Poland may contribute to a better understanding of the poorly known German experiments with ballistic missiles. The Polish lands are particularly interesting in this regard, as they were training grounds for rocket experiments at the end of World War II.

Efficient numerical description of the dynamics of interacting multispecies quantum gases

We present a highly efficient method for the numerical solution of coupled Gross–Pitaevskii equations describing the evolution dynamics of a multi-species mixture of Bose–Einstein condensates in time-dependent potentials. This method, based on a moving and expanding reference frame, compares favorably to a more standard but much more computationally expensive solution based on a frozen frame. It allows an accurate description of the long-time behavior of interacting, multi-species quantum mixtures including the challenging problem of long free expansions relevant to microgravity and space experiments. We demonstrate a successful comparison to experimental measurements of a binary Rb–K mixture recently performed with the payload of a sounding rocket experiment.

Development and suborbital validation of technologies for direct imaging of nearby exoplanetary systems in reflected visible wavelengths

Primarily through indirect observational techniques, the existence of thousands of exoplanetary systems has been confirmed. However, we still do not have an image of an exoplanetary system in reflected visible light. This is important because planetary systems as old as the solar system (∼5 G yr) have cooled to near equilibrium and are thus no longer as bright as the systems being detected by current infrared coronagraphs. Furthermore, the visible bandpass contains valuable information about aerosols, hazes, and clouds that are unavailable to infrared investigations.Our research group has transitioned key technologies that are necessary for direct imaging of exoplanets and their environments from laboratory to near space using suborbital platforms. Two of our sounding rocket experiments, called Planetary Imaging Concept Testbed Using a Rocket Experiment (PICTURE) and Planet Imaging Coronagraphic Technology Using a Reconfigurable Experimental Base (PICTURE-B), matured a 0.5m diameter Gregorian telescope, a (600nm to 750nm) visible nulling coronagraph (VNC), a 1024 channel deformable mirror (DM) and a fine pointing system.Following up on these rocket experiments, in 2019 we flew a high-altitude balloon called Planetary Imaging Concept Testbed Using a Recoverable Experiment - Coronagraph (PICTURE-C). It carried a telescope employing a 0.6m diameter Off Axis Parabolic (OAP) primary mirror, a vector vortex coronagraph (VVC), a 97-channel low order and a 1024 element high order DM operating in the 540nm to 660nm wavelength range. Like the rocket experiments, the first balloon flight demonstrated a 5 milliarcseconds (mas) fine pointing capability and the space worthiness of the coronagraph.The latest flight of PICTURE-C occurred on September 28 2022. It was designed to obtain the first high contrast (∼10−6) image of a debris disk, a circumstellar ring produced by the sublimation of cometary material and collisions among asteroids, comets and Kuiper-belt analogs, in reflected visible light. The experiment achieved 1 mas root mean square (RMS) fine pointing stability. Even though unanticipated transient vibrations prevented PICTURE-C from attaining its science goals, the conronagraph demonstrated 4×10−6 contrast over 540nm to 660nm (20% bandwidth).

A Spherical Shells Model of Atmospheric Absorption for Instrument Calibration

We present a model for atmospheric absorption of solar ultraviolet (UV) radiation. The initial motivation for this work is to predict this effect and correct it in Sounding Rocket (SR) experiments. In particular, the Full-sun Ultraviolet Rocket Spectrograph (FURST) is anticipated to launch in mid-2023. FURST has the potential to observe UV absorption while imaging solar spectra between 120-181 nm, at a resolution of , and at altitudes of between ≈ 110-255 km. This model uses estimates for density and temperature, as well as laboratory measurements of the absorption cross-section, to predict the UV absorption of solar radiation at high altitudes. Refraction correction is discussed and partially implemented but is negligible for the results presented. Absorption by molecular Oxygen is the primary driver within the UV spectral range of our interest. The model is built with a wide range of applications in mind. The primary result is a method for inversion of the absorption cross-section from images obtained during an instrument flight, even if atmospheric observations were not initially intended. The potential to obtain measurements of atmospheric properties is an exciting prospect, especially since sounding rockets are the only method currently available for probing this altitude in-situ. Simulation of noisy spectral images along the FURST flight profile is performed using data from the High-Resolution Telescope and Spectrograph (HRTS) SR and the FISM2 model for comparison. Analysis of these simulated signals allows us to capture the Signal-to-Noise Ratio (SNR) of FURST and the capability to measure atmospheric absorption properties as a function of altitude. Based on the prevalence of distinct spectral features, our calculations demonstrate that atmospheric absorption may be used to perform wavelength calibration from in-flight data.

The Potential of the Wavelength-integrated Scattering Polarization of the Hydrogen Lyα Line for Probing the Solar Chromosphere

The intensity and the linear scattering polarization profiles of the hydrogen Lyα line encode valuable information on the thermodynamic and magnetic structure of the upper layers of the solar chromosphere. The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) sounding rocket experiment provided unprecedented spectropolarimetric data of this line, as well as two-dimensional broadband images in intensity and linear polarization. We theoretically investigate the potential of the Lyα broadband polarimetric signals for probing the solar chromosphere and its magnetic fields. We analyze the synthetic Stokes profiles obtained from a series of radiative transfer (RT) calculations out of local thermodynamic equilibrium, considering semi-empirical one-dimensional models of the solar atmosphere. The wavelength-integrated linear polarization signal is found to be dominated by the contribution from the wings when considering a Gaussian weighting function with a FWHM that corresponds to the CLASP slit-jaw broadband filter. These broadband linear polarization signals are strongly sensitive to magnetic fields of strengths on the order of 50 G, via the action of magneto-optical (MO) effects, and are expected to encode information on the middle–upper chromosphere. The two-dimensional broadband intensity and linear polarization images observed by CLASP can be suitably mimicked using synthetic wavelength-integrated signals obtained considering atmospheric models and magnetic fields that are representative of solar regions with different levels of activity, provided that the impact of MO effects is taken into account. Despite the limitations of a one-dimensional RT modeling, this work illustrates the diagnostic potential of filter-polarimetric Lyα signals for probing the solar chromosphere and its magnetism.

The First Flight of the Marshall Grazing Incidence X-Ray Spectrometer (MaGIXS)

The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) sounding rocket experiment launched on 2021 July 30 from the White Sands Missile Range in New Mexico. MaGIXS is a unique solar observing telescope developed to capture X-ray spectral images of coronal active regions in the 6–24 Å wavelength range. Its novel design takes advantage of recent technological advances related to fabricating and optimizing X-ray optical systems, as well as breakthroughs in inversion methodologies necessary to create spectrally pure maps from overlapping spectral images. MaGIXS is the first instrument of its kind to provide spatially resolved soft X-ray spectra across a wide field of view. The plasma diagnostics available in this spectral regime make this instrument a powerful tool for probing solar coronal heating. This paper presents details from the first MaGIXS flight, the captured observations, the data processing and inversion techniques, and the first science results.

Generation of Post Sunset E Region Electron Density Stratifications at the Magnetic Equator: An Analysis Using In Situ Measurements and Theoretical Estimations

AbstractMeasurements of electron density/irregularities and ion drift velocity/neutral wind were undertaken with Electron Density and Neutral Wind (ENWi) payload on‐board an RH300 flight on 6 April 2018 as part of the Sounding Rocket Experiment (SOUREX1). The presence of a clearly structured ENWi measured electron density profile is an interesting feature observed on this day. Concurrently electron density/irregularities are measured by a Langmuir probe payload which confirmed the presence of stratifications in electron density. The neutral wind measurements by ENWi also reveal a structured pattern. The hodograph analysis of the neutral wind components reveals clockwise rotation indicating downward phase propagation characteristics associated with the gravity waves. Analysis of the requisite ion convergence at the magnetic equator for occurrence of electron density stratifications using the observed electron density structures during the post sunset hours in relation to the ion convergence due to gravity wave winds is performed according to earlier theoretical simulations. This analysis reveals that conditions favoring the formation of stratification related ion convergence are present therein. Thus the present study for first time uses actual measurements of neutral winds and electron densities from same instrument to demonstrate the role of gravity wave induced winds in producing ion convergence at the magnetic equatorial region Trivandrum in the post sunset hours.

Modeling of solidification processes under consideration of particle transport in the melt under terrestrial and microgravity conditions

In this work the interaction of solid particles with the moving water-ice solidification front under terrestrial and microgravity conditions is studied by numerical simulations as well as by experiments. A global, three-dimensional, time-dependent model is used to simulate the solidification processes taking into account buoyant convection and the injection of the particles, their transport through the fluid and their interaction with the moving interface. In basic parameter studies without considering any particle transport and interaction, the thermal conditions of the solidification processes in the module were systematically varied and their influence on the position and shape of the solidification front investigated. It was found that there is only a minor influence on the pure solidification process whether the experiments are carried out under terrestrial or microgravity conditions. Also, the orientation of gravity relative to the solidification direction plays only a minor role. For the simulation of the TEXUS 56 sounding rocket experiment, the injection of the particles, their transport through the fluid and their interaction with the interface were considered in the simulations. The simulation results of the TEXUS 56 experiment agree reasonably to the experimental data. In both cases, a transition from a convex to a concave solidification front is observed. The calculated and measured growth rates are also in the same range and finally it was confirmed by the model that the injection of the particles causes a forced flow, which disturbs the solidification process for a short time period. Once the injection process is stopped, the forced flow decays quickly. The resulting particle distribution is comparable in experiment and simulation and no significant particle movement in the fluid is observed.

Numerical model for sessile drop evaporation on heated substrate under microgravity

• One-sided numerical model is developed for sessile drop evaporation on heated substrate under microgravity. • Flow motion is analyzed by 3D resolved computations of evaporating sessile drop. • Transition from primary to secondary instability occurs at critical aspect ratio. • First time fine effects of secondary instabilities on evaporation rate are captured. Although sessile drops have simple geometries, the physics involved in their evaporation process is complex owing to their numerous intricate interactions and their fluid nature. An accurate quantitative model of the evaporation process will enable increased understanding and control over the process. In this study, a numerical model is developed for sessile drop evaporation on a heated substrate under microgravity based on the results of rocket and parabolic experiments to understand the ’internal dynamics of a sessile drop. The model is quantitatively validated through experiments. Subsequently, a correlation between substrate temperature and evaporation rate is suggested for an ethanol sessile drop. The flow motion is analyzed by conducting three-dimensional resolved computations of an evaporating sessile drop. This provides insights into the Marangoni effect in the dynamics of the evaporation process and the occurrence of secondary instabilities. For the first time, the fine effects of secondary instabilities on the evaporation rate are captured. Our numerical model is valid in the absence of convection in the vapor phase, producing an interface of an evaporating drop in a fully saturated vapor, which typically exists under microgravity conditions.

Numerical Simulations of the First Stage of Dynamics of a High-Speed Plasma Jet in Fluxus and North Star Active Geophysical Rocket Experiments

Numerical Simulations of the First Stage of Dynamics of a High-Speed Plasma Jet in Fluxus and North Star Active Geophysical Rocket Experiments

Attitude Determination in Space with Ambient Light Sensors using Machine Learning for Solar Cell Characterization

Exploration of novel thin‐film solar cell technologies outreaches for their application in space. For extraterrestrial tests, irradiance conditions must be well determined to extract quantitative solar cell performances. Here, a new method for solar position determination is presented, based on parallelized ambient light sensor measurements is presented obtained from the sounding rocket experiment Organic and Hybrid Solar Cells In Space during the MAPHEUS‐8 mission. The solar position evolution is optimized using stochastic and gradient‐based methods in a Bayesian approach. Comparison with independent positioning estimates shows compelling agreement, lying mostly within 5° deviation. The inclusion of a simple Earth irradiation component mitigates a small systematic offset. Further, solution uncertainties are estimated with Monte‐Carlo Markov‐chain sampling. The point‐source irradiation model's accuracy can compete with that of a camera‐based trajectory. During equatorial Sun positions, the method's precision appears even higher––the 1σuncertainty of the derived solar position is as small as 3° for the effective angular deviation. This simple sensor array triangulation method being complementary to other attitude determination methods shows reasonable accuracies and allows implementation in systems of limited computational capabilities to determine the solar position or irradiance conditions for space or terrestrial solar cell applications.

The faintest solar coronal hard X-rays observed with FOXSI

Context. Solar nanoflares are small impulsive events releasing magnetic energy in the corona. If nanoflares follow the same physics as their larger counterparts, they should emit hard X-rays (HXRs) but with a rather faint intensity. A copious and continuous presence of nanoflares would result in a sustained HXR emission. These nanoflares could deliver enormous amounts of energy into the solar corona, possibly accounting for its high temperatures. To date, there has not been any direct observation of such persistent HXRs from the quiescent Sun. However, the quiet-Sun HXR emission was constrained in 2010 using almost 12 days of quiescent solar off-pointing observations by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). These observations set 2σ upper limits at 3.4 × 10−2 photons s−1 cm−2 keV−1 and 9.5 × 10−4 photons s−1 cm−2 keV−1 for the 3–6 keV and 6–12 keV energy ranges, respectively. Aims. Observing faint HXR emission is challenging because it demands high sensitivity and dynamic range instruments. The Focusing Optics X-ray Solar Imager (FOXSI) sounding rocket experiment excels in these two attributes when compared with RHESSI. FOXSI completed its second and third successful flights (FOXSI-2 and -3) on December 11, 2014, and September 7, 2018, respectively. This paper aims to constrain the quiet-Sun emission in the 5–10 keV energy range using FOXSI-2 and -3 observations. Methods. To fully characterize the sensitivity of FOXSI, we assessed ghost ray backgrounds generated by sources outside of the field of view via a ray-tracing algorithm. We used a Bayesian approach to provide upper thresholds of quiet-Sun HXR emission and probability distributions for the expected flux when a quiet-Sun HXR source is assumed to exist. Results. We found a FOXSI-2 upper limit of 4.5 × 10−2 photons s−1 cm−2 keV−1 with a 2σ confidence level in the 5–10 keV energy range. This limit is the first-ever quiet-Sun upper threshold in HXR reported using ∼1 min observations during a period of high solar activity. RHESSI was unable to measure the quiet-Sun emission during active times due to its limited dynamic range. During the FOXSI-3 flight, the Sun exhibited a fairly quiet configuration, displaying only one aged nonflaring active region. Using the entire ∼6.5 min of FOXSI-3 data, we report a 2σ upper limit of ∼10−4 photons s−1 cm−2 keV−1 for the 5–10 keV energy range. Conclusions. The FOXSI-3 upper limits on quiet-Sun emission are similar to that previously reported, but FOXSI-3 achieved these results with only 5 min of observations or about 1/2600 less time than RHESSI. A possible future spacecraft using hard X-ray focusing optics like those in the FOXSI concept would allow enough observation time to constrain the current HXR quiet-Sun limits further, or perhaps even make direct detections. This is the first report of quiet-Sun HXR limits from FOXSI and the first science paper using FOXSI-3 observations.